The present invention relates generally to an arrangement in which filaments produced from heat softenable material are quenched by passing a gaseous quenching medium over the filaments as they are discharged from the orifices of an extruding die.
Filaments formed of synthetic polymer and the like such as, for example, synthetic yarn filaments, are typically formed by forcing molten polymer material through a plurality of openings or orifices in an extrusion die so that the molten material leaves each opening in the die as an individual strand or filament. When the material initially exits an opening in the extrusion die, it is still in a molten state, and it is generally known that these filaments must be quenched or cooled to convert the molten material to a hardened material, and with most filaments the quenching should preferably occur as soon as the molten filaments leave the die.
The particular apparatus used to quench molten filaments takes a variety of forms. For example, so-called quench sticks made of porous materials such as ceramics or sintered metals have been used as described, for example, in Stofan U.S. Pat. No. 3,969,482; Barnett U.S. Pat. No. 3,135,811; and Boyes U.S. Pat. No. 4,038,357, wherein the porous material is disposed within an annular pattern of vertically flowing filaments and extend generally from the extrusion die for a considerable distance below the die. In Morrell U.S. Pat. No. 2,730,758, cooling air is directed vertically upwardly by a jet disposed within the annular pattern of filaments so that the air strikes a discoidal deflector plate located immediately below the die whereby the air is deflected outwardly toward and through the filaments, and U.S. Pat. No. 3,695,858; U.S. Pat. No. 3,959,052; and Japanese Pat. Nos. 38-7511 and 51-7218 all disclose other variations of gaseous flow patterns extending generally across the vertically extending filaments.
Japanese Patent Nos. 46-34926 and 47-21251 disclose two similar versions of a quenching apparatus that includes a large plurality of vertical stacked discs having spacings therebetween through which the quenching gas is discharged radially over a substantial length of the vertically extending filaments, and the flow of the quenching gas from each of the spacings between the discs is controlled by the size of the openings in the center of the discs through which the quenching air flows to the radial spacings. In both of these patents, the quenching air is intended to flow radially and perpendicular to the vertically extending filaments, although in the first-listed patent there is a suggestion that the discs can be modified in some undescribed way to cause the air to flow at some undefined angle other than perpendicular to the filaments. Similarly, in Miani U.S. Pat. No. 4,259,048, a single discoidal nozzle is positioned immediately beneath the die and within the annular pattern of filaments, and the discoidal nozzle is specially formed to define at its periphery a single annular slit directed perpendicular to the vertical direction of extrusion of the filaments to provide a single laminar centralized discoidal jet of cooling air that impinges perpendicularly adjacent the just extruded filaments close to the holes in the die. Finally, commercial apparatus has been available which includes a quenching system having a discoidal nozzle formed with a single annular slot that directs the quenching air upwardly toward the lower surface of the die at a predetermined upward angle with respect to the horizontal, and while this nozzle overcomes or alleviates drawbacks of the perpendicularly directed flow of the nozzle disclosed in the aforesaid Miani patent, the single quenching air flow is difficult to properly control in terms of being able to obtain both a proper velocity and quantity of quenching air.
With regard to most filaments, it is important in terms of the quality of the filament that is to be produced that the filaments in the annular pattern of filaments be cooled as uniformly as possible as soon as they leave the die. As the size of dies increases and as the number of filament forming openings in a die increase, it becomes more difficult to obtain uniform cooling of all of the filaments. For example, where the cooling air is directed radially outwardly from the center of the annular pattern of filaments in a direction perpendicular to the vertical extent of the filaments, as disclosed in the aforesaid Miani patent, the quenching air immediately cools those filaments which are located at the radially innermost portion of the filaments in the annular pattern, but as the quenching air progresses outwardly through the annular pattern of filaments, the downward drag exerted in the quenching air by the rapidly flowing filaments tends to direct the quenching air downwardly so that by the time the quenching air actually reaches the outermost portion of the annular pattern, it is located substantially below the bottom face of the die. This can result in these outermost filaments not being cooled quickly enough and can adversely affect the uniformity of the size and consistency of the filament which, in turn, affects the performance of the filaments, and the "hand" of the filaments if they are to be used as synthetic yarn. This adverse affect can sometime be partially affected by increasing the velocity of the quenching air as it leaves the nozzle so that it reaches the outermost filaments more quickly, but if the exit velocity of the quenching air is too high, it can actually break the innermost filaments. Where the quenching gas is concentrated in a single nozzle, as discussed above, it is much more difficult to control the air flow so that it obtains a proper balance between velocity and the quantity of the air flow.
In accordance with the present invention a unique quenching apparatus is provided which addresses and alleviates some of the problems with known apparatus of this type.